1. Field of the Invention
The present invention relates to a suspension board with circuit and, more particularly, to a suspension board with circuit used for a hard disc driver.
2. Description of the Prior Art
A suspension board with circuit used for a hard disc driver is a circuit board in which lines of wire for connecting between a magnetic head and a read/write board to which read/write signals to be read and written by the magnetic head are transmitted are integrally formed in the suspension board suspending the magnetic head. This suspension board with circuit can suspend the magnetic head mounted thereon to keep its good floating position, with a minute interval between the magnetic head and a magnetic disk being held against an airflow generated when the magnetic head and the magnetic disk run relative to each other. Due to this, the suspension board with circuit is becoming widely used.
This suspension board with circuit usually comprises a metallic supporting plate 1 formed of a stainless foil, a base layer 2 formed of an insulating material formed on the metallic supporting plate 1, a conductive layer 3 formed on the base layer 2 in the form of a specific circuit pattern, and a cover layer 4, formed of an insulating material, for covering the conductive layer 3, as shown in FIG. 21. Also, the suspension board has external connection terminals 5 formed to connect the lines wire formed in the form of the circuit pattern with the read/write board 9.
The external connection terminals 5 have pad portions 8 comprising e.g. a nickel plated layer 6 and a gold plated layer 7 formed in sequence by plating on the conductive layer 3 exposed by opening the cover layer 4. The terminals 10 of the read/write board 9 and the pad portions 8 are superimposed with each other and are bonded to each other in the superimposed state, for example, by applying supersonic vibration from the outside of the metallic supporting plate 1 (as indicated by an arrow in FIG. 21), as indicated by a phantom line.
With this connection between the external connection terminals 5 and the terminals 10 of the read/write board 9, since the supersonic vibration which is applied from the outside of the metallic supporting plate 1 is transmitted from the metallic supporting plate 1 to the pad portions 8 through the base layer 2 and the conductive layer 3, the vibration is damped until it reaches the pad portions 8. As a result of this, the vibration damped sometimes may not be strong enough to bond the terminals to each other. Because of this, the terminals sometimes cannot be bonded to each other with sufficient strength and, thus, sufficient bonding reliability sometimes may not be obtained.
On the other hand, it may be conceivable that the supersonic vibration is applied from the outside of the read/write board 9 at a side thereof at which the terminals 10 are formed, but the read/write board 9 is usually so large in thickness that the supersonic vibration cannot be transmitted with ease. Thus, in this case also, the terminals still cannot be bonded to each other with sufficient strength.
It is the object of the present invention to provide a suspension board with circuit that enables its terminals to be bonded to the other terminals with sufficient strength with simple structure, to ensure sufficient bonding reliability.
A suspension board with circuit of the present invention comprises a metal supporting layer, an insulating layer formed on the metal supporting layer and a conductive layer formed on the insulating layer and has a terminal portion formed to connect with an external circuit, wherein the terminal portion is formed without the metal supporting layer and/or the insulating layer being formed.
According to the suspension board with circuit of the present invention, since both of the metal supporting layer and the insulating layer or either of them are not formed at the terminal portion, in the case where the terminal portion is bonded to an external circuit, for example when external force such as supersonic vibration and equivalent is applied from the outside of the metal supporting layer or the insulating later, the external force such as the supersonic vibration is transmitted to the bonded portion without passing through both of or either of the metal supporting layer and the insulating layer. Thus, the vibration is transmitted to the bonded portion with little damped external force. Hence, the both terminals can be bonded to each other with higher strength to thereby produce improved bonding reliability therebetween.
In the suspension board with circuit of the present invention, preferably, the terminal portion may be substantially formed by the insulating layer, the conductive layer formed on the insulating layer and a pad portion formed on the conductive layer, may be substantially formed by the metal supporting layer, the conductive layer formed on the metal supporting layer and the pad portion formed on the conductive layer, or may be substantially formed by the conductive layer and the pad portion formed on the conductive layer.